M.Sc. Moritz Schaar

Fraunhofer-Einrichtung für Individualisierte und Zellbasierte Medizintechnik IMTE
Mönkhofer Weg 239a
23562 Lübeck

Email:	moritz.schaar(at)imte.fraunhofer.de
Phone:

Roles

Research Assistant

Research

Research Interests

Computed Tomography
Nuclear Imaging
Medical Image Processing

Involved Projects

Curriculum Vitae

MORITZ SCHAAR was born in Halle/Saale, Germany in 1988. He received his Master of Science in Medical Engineering Science in 2013 from the University of Lübeck, Germany. During his study he was mainly interested in medical imaging and medical image processing. In 2013 he wrote his master thesis at the Philips Technologie GmbH – Innovative Technologies, Research Laboratories in Hamburg about rib segmentation in thorax radiographies. Since 04/2014 he is a student of the Graduate School for Computing in Medicine and Life Sciences and works in the field of combined reconstruction of Computed Tomography and Nuclear Medical Imaging in cooperation with the MiE medical imaging electronics GmbH in Seth, Germany.

The project is financially supported by the TANDEM II project (grant no. 122 13 002).

Publications

[ 2023 ]
[ 2020 ]
[ 2019 ]
[ 2017 ]
[ 2013 ]

2023[ to top ]

Hellwege, L., Schaar, M., Buzug, T. M. and Stille, M.: Advanced Empirical Dual-Energy Calibration, 2023.
- [ BibTeX ]
@inproceedings{hellwege2023advanced, author = {Hellwege, Laura and Schaar, Moritz and Buzug, Thorsten M. and Stille, Maik}, booktitle = {Proceedings of IEEE MIC 2023}, keywords = {buzugthorsten}, publisher = {IEEE Xplore}, title = {Advanced Empirical Dual-Energy Calibration}, year = 2023 }
Hellwege, L., Schaar, M., Buzug, T. and Stille, M.: Enhancing virtual monoenergetic images for non-congruent dual-energy CT projection data, Current Directions in Biomedical Engineering, 9, 674–677, 2023, DOI: 10.1515/cdbme-2023-1169.
- [ BibTeX ]
@article{article, author = {Hellwege, Laura and Schaar, Moritz and Buzug, Thorsten and Stille, Maik}, journal = {Current Directions in Biomedical Engineering}, keywords = {buzugthorsten}, month = {09}, pages = {674-677}, title = {Enhancing virtual monoenergetic images for non-congruent dual-energy CT projection data}, volume = 9, year = 2023 }

2020[ to top ]

Bolke, A., Zvolsky, M., Kohlhase, N., Seeger, S., Schaar, M. and Rafecas, M.: Modelling of a Bi-Modal PET / Compton-Camera System for Non-Pure Positron Emitters, 1–3, 2020, DOI: 10.1109/NSS/MIC42677.2020.9507915.
- [ BibTeX ]
- [ URL ]
@inproceedings{Bolke2020, abstract = {In this work, we investigate the combination of two imaging modalities, positron emission tomography (PET) and Compton-camera (CC) imaging. A prototype for simultaneous PET/CC acquisition was simulated. The design is based on the combination of two existing prototypes and allows for a first investigation of the bi-modal acquisition of the radionuclides <sup>89</sup>Z<inf>r</inf> and <sup>124</sup>I. Since the simulation framework GATE is not able to properly output coincidences of such a bi-modal system, a post-processing tool was developed. This includes custom coincidence sorting and classification of PET and CC data. Here we present our postprocessing pipeline as well as our first results, and discuss the implications of the coincidence logic and the fraction of randoms on the data. The availability of such data is the prerequisite for developing novel image reconstruction approaches.}, author = {Bolke, A. and Zvolsky, M. and Kohlhase, N. and Seeger, S. and Schaar, M. and Rafecas, M.}, booktitle = {2020 {IEEE} Nuclear Science Symposium and Medical Imaging Conference ({NSS}/{MIC})}, keywords = {PET}, month = 10, pages = {1-3}, title = {Modelling of a Bi-Modal PET / Compton-Camera System for Non-Pure Positron Emitters}, year = 2020 }
Kohlhase, N., Wegener, T., Schaar, M., Bolke, A., Etxebeste, A., Sarrut, D. and Rafecas, M.: Capability of MLEM and OE to Detect Range Shifts with a Compton Camera in Particle Therapy, IEEE Transactions on Radiation and Plasma Medical Sciences, 4(2), 233–242, 2020, DOI: 10.1109/TRPMS.2019.2937675.
- [ BibTeX ]
- [ URL ]
@article{8815866, abstract = {To identify range deviations by using Compton cameras (CC), tomographic image reconstruction of CC data is needed. Within this context, image reconstruction is usually performed using Maximum Likelihood Expectation Maximization (MLEM), and more recently, the Origin Ensemble (OE) algorithm. In this work, we investigate how MLEM and OE affect the precision and accuracy of estimated range deviations. In particular, we focus on the effects of data selection, statistical fluctuations, and artifact reduction. The use of external information of the beam path through a hodoscope was also explored. Additionally, two methods to calculate range deviations were tested. To this aim, realistic proton beams were simulated using GATE and data from single spots as well as from 7 contiguous spots of an energy layer were reconstructed. MLEM and OE reacted differently to the poor data statistics. In general, both algorithms were able to detect range shifts for single spots, particularly when multiple coincidences were also considered. Selection of events corresponding to the most relevant energy peaks decreased the identification performance due to the lower statistics. When data from several contiguous spots were jointly reconstructed, the accuracy of the results degraded significantly, and non-zero shifts were assigned when no shifts had occurred. The limited size of the cameras and the subsequent restriction in the orientation and aperture of detected cones, as well as in the number of detected events are major challenges. Future efforts should be devoted to noise regularization and compensation for data truncation.}, author = {{Kohlhase}, N. and {Wegener}, T. and {Schaar}, M. and {Bolke}, A. and {Etxebeste}, A. and {Sarrut}, D. and {Rafecas}, M.}, journal = {IEEE Transactions on Radiation and Plasma Medical Sciences}, keywords = {KohlhaseNadja}, month = {03}, number = 2, pages = {233-242}, title = {Capability of MLEM and OE to Detect Range Shifts with a Compton Camera in Particle Therapy}, volume = 4, year = 2020 }

2019[ to top ]

Schaar, M. and Rafecas, M.: Modelling of Scatter in the System Matrix for 3D PET Image Reconstruction: a Comparative Study, 2019, DOI: 10.1109/nss/mic42101.2019.9059797.
- [ BibTeX ]
@inproceedings{Schaar2019, author = {Schaar, M. and Rafecas, M.}, booktitle = {2019 {IEEE} Nuclear Science Symposium and Medical Imaging Conference ({NSS}/{MIC})}, keywords = {IMT}, month = 10, publisher = {{IEEE}}, title = {Modelling of Scatter in the System Matrix for 3D PET Image Reconstruction: a Comparative Study}, year = 2019 }
Zvolsky, M., Schreiner, N., Seeger, S., Schaar, M., Rakers, S. and Rafecas, M.: Digital Zebrafish Phantom based on Micro-CT Data for Imaging Research, 2019, DOI: 10.1109/nss/mic42101.2019.9059702.
- [ BibTeX ]
@inproceedings{Zvolsky2019, author = {Zvolsky, M. and Schreiner, N. and Seeger, S. and Schaar, M. and Rakers, S. and Rafecas, M.}, booktitle = {2019 {IEEE} Nuclear Science Symposium and Medical Imaging Conference ({NSS}/{MIC})}, keywords = {IMT}, month = 10, publisher = {{IEEE}}, title = {{Digital Zebrafish Phantom based on Micro-CT Data for Imaging Research}}, year = 2019 }
Kohlhase, N., Wegener, T., Schaar, M., Bolke, A. and Rafecas, M.: Bildrekonstruktion von Compton-Kamera Daten unter Verwendung eines Hodoskops für die Reichweitenverifikation in der Partikeltherapie, 317, 2019.
- [ BibTeX ]
- [ URL ]
@inproceedings{kohlhase2019bildrekonstruktion, author = {Kohlhase, N and Wegener, T and Schaar, M and Bolke, A and Rafecas, M}, booktitle = {50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Abstractband}, editor = {Gromoll, Christian and Wegner, Niels}, keywords = {KohlhaseNadja}, organization = {Deutsche Gesellschaft für Medizinische Physik}, pages = 317, title = {Bildrekonstruktion von Compton-Kamera Daten unter Verwendung eines Hodoskops für die Reichweitenverifikation in der Partikeltherapie}, year = 2019 }
Zvolský, M., Seeger, S., Schmidt, C., Bruhn, D., Schaar, M., Weller, D. and Rafecas, M.: Nukleare in-vivo Bildgebung von Zebrafischen, 35, 2019.
- [ BibTeX ]
- [ URL ]
@inproceedings{zvolsky2019nukleare, author = {Zvolský, M and Seeger, S and Schmidt, C and Bruhn, D and Schaar, M and Weller, D and Rafecas, M}, booktitle = {50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Abstractband}, editor = {Gromoll, Christian and Wegner, Niels}, keywords = {imt}, pages = 35, title = {Nukleare in-vivo Bildgebung von Zebrafischen}, year = 2019 }
Zvolsky, M., Seeger, S., Schaar, M., Schmidt, C. and Rafecas, M.: MERMAID - A PET Prototype for Small Aquatic Animal Imaging, 2019, DOI: 10.1109/nss/mic42101.2019.9059687.
- [ BibTeX ]
@inproceedings{Zvolsky2019a, author = {Zvolsky, M. and Seeger, S. and Schaar, M. and Schmidt, C. and Rafecas, M.}, booktitle = {2019 {IEEE} Nuclear Science Symposium and Medical Imaging Conference ({NSS}/{MIC})}, keywords = {IMT}, month = 10, publisher = {{IEEE}}, title = {{MERMAID - A PET Prototype for Small Aquatic Animal Imaging}}, year = 2019 }
Wegener, T., Kohlhase, N., Schaar, M., Bolke, A. and Rafecas, M.: Stochastic behavior of the Origin-Ensemble Algorithm – effect on ange verification in proton therapy using Compton-Cameras, 240, 2019.
- [ BibTeX ]
- [ URL ]
@inproceedings{wegener2019stochastic, author = {Wegener, T and Kohlhase, N and Schaar, M and Bolke, A and Rafecas, M}, booktitle = {50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Abstractband}, editor = {Gromoll, Christian and Wegner, Niels}, keywords = {KohlhaseNadja}, organization = {Deutsche Gesellschaft für Medizinische Physik}, pages = 240, title = {Stochastic behavior of the Origin-Ensemble Algorithm – effect on ange verification in proton therapy using Compton-Cameras}, year = 2019 }

2017[ to top ]

Schaar, M., Buzug, T. M. and Rafecas, M.: PET image reconstruction using the Origin Ensemble algorithm and geometric constraints, 549–553, 2017, DOI: 10.1515/cdbme-2017-0115.
- [ BibTeX ]
@inproceedings{schaar2017oebmt, author = {Schaar, Moritz and Buzug, Thorsten M. and Rafecas, Magdalena}, booktitle = {Deutsche Gesellschaft für Biomedizinische Technik Jahrestagung, Dresden, Sept. 10–13, 2017}, journal = {Current Directions in Biomedical Engineering}, keywords = {PET}, number = 2, pages = {549-553}, publisher = {De Gruyter}, title = {PET image reconstruction using the Origin Ensemble algorithm and geometric constraints}, type = {Publication}, volume = 3, year = 2017 }

2013[ to top ]

Schaar, M. and Erhardt, J.: Segmentation of Anatomical Structures using Statistical Shape Models based on Level Sets, 2013.
- [ BibTeX ]
@inproceedings{Schaar2013, author = {Schaar, M. and Erhardt, J.}, booktitle = {Student Conference Medical Engineering Science}, keywords = {SchaarMoritz}, title = {Segmentation of Anatomical Structures using Statistical Shape Models based on Level Sets}, year = 2013 }